Patent GB-348590-A (GB)
Title: Improvements in and relating to electric switchgear
IPC: H01H71/52
Filed: 1929-11-14
Abstract: 348,590.. Automatic circuit-breakers and controllers. COX, F. B., 65, Flee Street, Liverpool. Nov. 14, 1929, No 34776. [Classes 38 (iii) and 38 (v).] No-volt release ; overload release.-In switch-gear of the type in which the no-volt, overload or like protective device comprises a percussive member set by the handle and adapted, when released by the operation of the protective device to open the switch by percussive action, the percussive member is provided directly or indirectly with a delay detent cam or like device adapted to hold it in operative relationship with the protective device until the operating handle and any parts actuated by it are moved clear of the percussive member, whereby when the switch is closed against no-volt and overload conditions, the percussive member when released, is free to make its full stroke to open the switch. As shown in Fig. 1, applied to switchgear of the type described in Specification 264,552, [Class 38 (iii), Electric motor control systems &c.], the handle A when moved to close the switch causes a pin a<4> to engage a projection c<4> on the percussive member C which carries the armature f<8> into engagement with the no-volt electromagnet F, the projection c<4> in turn engaging a pin b4 on the switch blade B and moving it into engagement with the fixed contacts b<1>. As the percussive member is operated it is latched in its operated position by a spring-controlled detent F so that no release of the switch can take place until the handle is fully returned to its " off " position in which the handle projection a<1> engaging the tail b<1> of the detent F so raising its hooked nose f<2> from the pin c<2> on the member C. This prevents the percussive member C from slowly following the handle A in its return movement owing to non-energization of the no-volt electromagnet E due to lack of voltage between the mains M, M<1> and ensures a release of the switch in such conditions, the unlatching of the member C enabling it to make a full unimpeded stroke in moving the switch blade B to the open position (Fig. 3). In a modification (Fig. 4), the switch B is combined with a star-delta starter the blade Bc of which is moved to engage the " starting " contacts S during the closing of the main switch blade B. In this form the detent F holding up the percussive member during the movement of the handle acts on the auxiliary switch blade Bc, which is operated directly by a cranked portion a<1> of the handle, a projection b<12> integral with the blade Bc engaging in turn the pin c<41> on the percussive member C, which as before has a projection c<4> acting on the pin b<4> of the blade B. The detent F is released by the handle A at the end of its return movement so permitting the blade Bc to be moved by its spring to engage the " running " contacts R and also to free the percussive member for action. In this form contacts f<5> in the no-volt circuit are arranged to be bridged as the detent F is moved out of engagement (Fig. 4B). Various other modifications are also described, the movement of the percussive member being held up until cleared by the handle by means of cams, toggle or other mechanisms. Further main and auxiliary switches and their associated mechanisms may be mounted on separate axes with interconnecting links and the switches may be arranged within metal casings fitted with external operating handles. In still another arrangement the handle in its return movement after closing the switch may be arranged to move over resistance contacts. Specification 280,271, [Class 38 (iii), Electric motor control systems &c.], also is referred to.